It is known to use vehicles to project concrete inside tunnels, on rock walls or on walls of constructions.
The vehicles must be able to move autonomously on roads and on uneven ground. For this reason, they usually have four or more drive wheels or tracks.
The vehicles are suitable for pumping and directing the concrete; they normally receive the concrete from a truck-mounted mixer, or a concrete mixer, and project it onto a wall, keeping the jet as perpendicular as possible to the wall and at the correct distance.
During the pumping phase, moreover, chemical additives can be added to the concrete to accelerate solidification.
These vehicles for projecting concrete can also have a tank containing water and a washing pump to wash the arm used for projecting the concrete at end of work.
In these known vehicles, the heat engine normally used to move them is also used for the pumping operations and for directing the concrete and for washing the arm.
This therefore remains switched on throughout the step of pumping and directing the concrete, at least until the work is finished, with consequent emission of exhaust fumes, noxious both for the health and also for the environment.
Furthermore, using the heat engine all the time the concrete is projected, and possibly subsequently washing, is a source of annoying noise for the workers, especially if the work is carried out in tunnels or other enclosed space.
A solution is also known, in the state of the art, in which the mechanical energy needed for the concrete pumping step comes from electromechanical conversion, carried out by a three-phase induction electric motor connected to the industrial electric mains when the vehicle is stationary and the energy is available.
However, this solution is limited because it has limited operating flexibility mainly due to the single power source, provided either by the heat engine or the external electric network, where present.
Another disadvantage concerns the fact that all the services performed by these vehicles, including the essential ones for moving the vehicle, moving the arm and pumping the concrete, and also the auxiliary ones, are actuated by hydraulic movements, using hydraulic pumps driven by the heat engine.
Document US 2009/095549 A 1 (US'549) describes a hybrid system for driving a vehicle, which uses electric and hydraulic components. The hybrid system in US'549 comprises a first main movement element, a drive transmission of the first main movement element, a rechargeable power source and a power take-off (PTO) device. The hybrid system also comprises a hydraulic motor in direct or indirect mechanical communication with the PTO and an electric motor in direct or indirect mechanical communication with the hydraulic motor. The electric motor can supply and receive power to/from the drive transmission of the first main movement element through the PTO. Again through the PTO, the hydraulic motor can supply and receive power to/from the drive transmission of the first main movement element.
A device is known, from CN 202 969 950 U (CN'950), for pumping concrete that comprises a traditional heat engine to move the frame of the vehicle, and an accumulation battery usable for pumping the concrete when the vehicle is stationary. CN'950 therefore describes a hybrid system of the conventional type.
Document CN 102 416 867 A (CN'867) describes a double power device for a vehicle, in which a traditional heat engine is used to move the vehicle, and an electric motor is used to drive the hydraulic pumps, if there is an electric energy source in the construction site. Otherwise, the heat engine itself drives the hydraulic pumps. CN'867 also describes a hybrid system of the conventional type.
One purpose of the present invention is to obtain a vehicle to project concrete able to perform all the essential services of moving, pumping the concrete and washing the arm, without needing to keep the heat engine switched on even if the external electric network is not available.
Another purpose of the present invention is to obtain a reduction in the consumption of fuel, for example diesel, and a reduction in the corresponding emissions, for example of carbon dioxide and particulate, thus reducing problems of costs and environmental pollution.
Another purpose is to obtain a reduction in noise and to safeguard the health of the people near said vehicles, including the workers on the site where the vehicles are situated.
Another purpose of the present invention is to improve the overall energy efficiency of said vehicles, replacing the diesel/hydraulic conversion chains by other conversion chains having a better performance.
The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.